What are live attenuated vaccines?

A live attenuated vaccine is like giving your body a gentle training session to fight off germs.

Imagine you're playing a game of tag with your friends. If you run full speed every time, it's super tiring, but if you just jog slowly at first, you get used to running and eventually can sprint without getting out of breath. That’s what live attenuated vaccines do: they use a weaker version of the germ that causes sickness, so your body can learn how to fight it without getting too sick.

The germ in the vaccine is still alive, that's why it's called "live", but it has been attenuated, which means it’s been made weaker. It acts like a friendly practice opponent, teaching your body how to recognize and attack the real germ when you meet it later.

Because the germ is still alive, your body gets a full training session. It learns all about the germ, what it looks like, how it moves, and how to stop it from making you sick. This helps your body build strong defenses that last for years.